@srikanthmee(@NFGDom), I appreciate your response. Unfortunately, I have already tried that, and it doesn't seem to dictate the order in the theme selector 

Even in the picture you sent, the order seems off. You have the order set as 'Green, Red, Blue, Purple', then in the screenshot, they show 'Green, Blue, Red, Purple'. 

 

The Service Now docs say the order field you referenced "specifies when the style is applied. The higher the order, the greater its priority is." It doesn't mention the order shown in the theme selector here either. 

 

Maybe your experience is by coincidence? If you change your order now, does it change it in the selector?